1. Field of the Invention
The present invention relates to APPARATUS FOR FORMING AND INSTALLING UNDERGROUND DRAINPIPE, and more particularly to improvements in apparatus capable of forming drainpipe from a roll of plastic sheet material and simultaneously installing such pipe at desired underground locations without requiring trenching or filling operations.
2. Description of the Prior Art
It has heretofore been known to form plastic drainpipe from a roll of sheet material as the formed pipe is being drawn through an underground passage, as exemplified by Australian Patent Application No. 31565/77 dated Dec. 14, 1977, the Applicant being Sanko Co., Ltd. and Nippo Co., Ltd., and the actual Inventors being Kenichiro Takagishi and Yutaka Tusda, the Inventors in the herein application.
As stated in said Australian application, although the invention is discussed in terms of drainage pipe, it also relates to situations in which the pipe is not perforated and is used to convey water to a required destination.
As set forth in said Australian application, drainage has been practiced since olden times for land reclamation or improvement. Development of covered drains has been especially remarkable in the last few decades. The conventional covered drain, in general, either comprises an underground tube or a drain tunnel without a liner. Such drain tunnels are conventionally constructed by propelling a bullet-like head or "mole" along a desired underground path to displace the soft earth outwardly and leave behind the cylindrical drain tunnel. These drain tunnels, however, collapse easily because no support means is provided. Also, since the drain must usually be at a comparatively shallow depth, the drain tunnel tends to collapse when heavy equipment passes over it.
In humid regions where the soil is extremely soft, the drain tunnel collapses, at least in part, and must be renewed every year, resulting in considerable time, expense and labor.
To prevent collapse of the drain tunnel, drains with support means have been developed. They are constructed by digging a trench, placing tile or plastic tubes in the trench and subsequently refilling the trench with soil. Clay tubes are guite heavy and come in relatively short sections so that installation is quite laborious. Plastic tubes are lighter in weight, longer and are of sufficiently high strength, but the trenching and filling operation still makes them expensive and slow to install.
The apparatus of the present invention avoids the described difficulties by forming and laying the drainpipe simultaneously without requiring trenching or filling. The apparatus is designed to form the pipe automatically from a rolled web of sheet plastic as the pipe is dragged along behind the mole through the underground passage formed thereby.
Means is provided for shielding the critical forming operation from dirt and debris which might otherwise fall into this area and impair the forming of the drainpipe. In this connection, it should be noted that the web is manufactured with a series of tongues along one side interengageable in cooperating slots in the other side, the tongues and slots serving to hold the pipe in its finished configuration when fully interengaged. Unwanted dirt or debris falling into the portion of apparatus which effects complete interlocking can often prevent the described interlocking of the tongues and slots from taking place.
It is also essential that proper tension and angle of approach be exerted on the web of sheet plastic material as it is drawn through the portion of the apparatus which curls it from flat condition into generally tubular condition, and means is provided for accomplishing the tensioning and directing functions.
It is therefore an object of the present invention to provide an apparatus for installing a covered drain of the character set forth which is capable of trouble free operation under adverse conditions.
Another object of the present invention is to provide an apparatus of the character set forth which is capable of easy removal and installation in depressions in the soil in alignment with the proposed run of the resulting underground drainpipe.
A further object of the present invention is to provide apparatus of the character set forth in which the web of plastic sheet material is drawn from the supply roll, flattened out, curled into tubular form, and the locking tongues or tabs engaged in their respective slots under controlled conditions of tension and angle of approach.
Other objects of the present invention will in part be obvious and will in part appear hereinafter. For a fuller understanding of the nature and objects of the present invention, reference should be had to the following detailed description, taken in connection with the accompanying drawings.